Given the expression for electric field intensity at a point due to a thin infinitely long straight wire. Give the meaning the of symbols used.

Explanation

Let The Gaussian surface be taken as a cylinder of legnth l and radius r. Electric field lines drawn from a point on the wire to every point on the rim of a circular plane make an angle of zero with respect to the normal drawn to te surface.
Electric flux through the Gaussian surface `= E(SA), SA=` surface area
`=E(2 pi l)`
If `lamda` represents linear charge density of the thin wire, the total charge `Sigmaq` on the wire `=lamdal`.
From Gauss Law, total outward electric flux through a closed surface `=1/(epsilon_(0))` (total charge enclosed)
i.e. `E (2 p l)=(lamda l)/(epsilon_(0))`
i.e. `E=(lamda)/(2 pi epsilon_(0)r)`
Vectroally, `vecE=((a))/( 2 pi epsilon_(0)r)hatn` where `hatn` is the radial unit vector in the plane normal to the wire passing through the point.